Truck Minor Vibration over 70 MPH?

You say the vibration is when coming down hill, have you thought it may be linked to your Jakes somehow.

 

Possible slop in the drivelines, maybe slip yokes.

 

Not sure how one associates a vibration with a leveling valve. Care to elaborate on the thought process behind this?

 

Suspension ride height is one of the most common areas of driveline vibration issues. If the ride height is high or low from spec the driveshafts and ujoint operating angles can be extreme and will cause a vibration that can come and go upon accell and decell. This type of vibration will usually be felt in your feet and it your seat, maybe the shifter as well.

The leveling valve is the valve the maintains the suspension ride height and is most often the adjustment point to set the desired ride height level. This is something that is easy to check and set and is always first on the list to check when troubleshooting a vibration complaint.

 

I'd start with the easy stuff first: tires(inflation, balance, out of round, flat spots) and then the shocks and then the alignment.

Good Luck!

 

Don’t forget wheels, check for bent rim, by spinning wheel against a stationary object. Aluminum’s can get distorted easier and quicker than you’d think. Especially steers.

 

I’m gonna guess it’s probably on or more of the wheel balances. Spin balancing being set on a machine, doesn’t mean it stays balanced at all speeds.I don’t know about Trucks, but high speed on the Car balancing with a machine is done when other techniques don’t work. never seen if done on a Truck only Cars.Centramatics or equal, maybe? Otherwise it may be one of the driveshafts, since only downhill. A loose u- joint or not enough angle ( set too low ) causing vibrations. Drive shafts aren’t balanced as good as they can be, from the factory.